RM0090: Reference manual - STMicroelectronics

Secure digital input/output interface (SDIO) RM0090
1. Select a card (SELECT/DESELECT_CARD, CMD7), if none is already selected.
2. Set the block length (SET_BLOCKLEN, CMD16) to 1 byte. Only the 8-bit card
lock/unlock byte (byte 0 in Table 147) is sent.
3. Send LOCK/UNLOCK (CMD42) with the appropriate data byte on the data line including
the 16-bit CRC. The data block indicates the mode (ERASE = 1). All other bits must be
zero.
4. When the ERASE bit is the only bit set in the data field, all card contents are erased,
including the PWD and PWD_LEN fields, and the card is no longer locked. When any
other bits are set, the LOCK_UNLOCK_FAILED error bit is set in the card status
register and the card retains all of its data, and remains locked.
An attempt to use a force erase on an unlocked card fails and the LOCK_UNLOCK_FAILED
error bit is set in the card status register.
28.4.11 Card status register
The response format R1 contains a 32-bit field named card status. This field is intended to
transmit the card status information (which may be stored in a local status register) to the
host. If not specified otherwise, the status entries are always related to the previously issued
command.
Table 134 defines the different entries of the status. The type and clear condition fields in the
table are abbreviated as follows:
Type:
● E: error bit
● S: status bit
● R: detected and set for the actual command response
● X: detected and set during command execution. The SDIO card host must poll the card
by issuing the status command to read these bits.
Clear condition:
● A: according to the card current state
● B: always related to the previous command. Reception of a valid command clears it
(with a delay of one command)
● C: clear by read
865/1416 Doc ID 018909 Rev 3